Plasma has long been employed to process substrates (e.g., wafers or flat panels) to form electronic products (e.g., integrated circuits or flat panel displays). Semiconductor wafers are typically placed in an etch chamber with a mask layer to direct the etch of underlying materials. The etching process removes the underlying materials not covered by the mask. Due to the volatile plasma conditions generated inside of a chamber, the etch process may also remove material from surfaces of parts within the plasma chamber. Over time, the parts inside the processing chamber will therefore wear and will accumulate particulate matter and/or etch residues, which may alter the etch performance and/or cause process drift. For this reason, in addition to the need to replace consumable parts, there is also a need to periodically perform wet clean operations (i.e., of the inside surfaces and/or parts of a chamber).
After a wet clean, the chamber must be reconditioned through various steps/processes (i.e., processed for wet clean recovery) before the chamber is allowed to proceed with production wafer processing. This process is sometimes referred to as chamber “seasoning.” Seasoning attempts to produce surface conditions that mimic a steady state. When steady state is achieved, the solution tends to be brittle, i.e. it is not always universal from process to process or chamber to chamber. Perhaps even worse, the seasoning itself can be a significant fraction of the total tool utilization, e.g. seasoning for 15-70 hours while the process only runs for 150-250 hours. Obviously, this is a productivity hit, not to mention wasted energy consumption, cost of seasoning wafers, and high cost of consumables as they wear just to season them. Furthermore, while a chamber recovers from a wet clean, fabrication of production wafers is stopped.
As is well known, etch and deposition reactors are very complex equipment with multiple variables to control correct wafer processing condition. In modern semiconductor processing, the system has grown so complex that it is non-trivial to explain different physical/chemical processes using set of trivial physical equations. Due to this complexity, it is difficult to model modern day etch/deposition processes in its full form with all gas/pressure/power/frequency inputs. This difficulty in modeling (and by extension predicting) has reduced plasma processing into an art which largely depends on the artist's experience level (in this case the engineer) and environment rather than a predictable science.
It is in this context that embodiments arise.